26.5 Installing a Power Supply

Standard
power supplies are secured with four screws. To remove a power
supply, disconnect the AC supply cord, the motherboard power
cable(s), and all device power cables. Use one hand to hold the power
supply in place while removing the four screws that secure it, and
then lift it straight out. Some power supplies use a locking tab and
slot arrangement, so you may have to slide the power supply a short
distance to clear the tab before lifting it out. To install a power
supply, reverse that process. Slide the power supply into place, as
shown in Figure 26-5, making sure that the locking
tab, if present, mates with the slot.

Figure 26-5. Sliding the power supply into position

Once the power supply is in place, align the screw holes and insert
the screws, as shown in Figure 26-6. If necessary,
support the power supply with one hand while you insert screws with
the other. Most good cases (such as the Antec KS-288 shown) have a
tray that supports the power supply, while other cases simply leave
the power supply hanging in midair, secured only by the screws. In
the latter situation, you may want to get someone to volunteer a
second pair of hands to hold the power supply while you insert the
screws, particularly if you're working in an awkward
position. We've seen at least one motherboard
damaged by a dropped power supply, which ripped the processor,
heatsink/fan, and socket right out the motherboard on its way past.

Figure 26-6. Securing the power supply by inserting the four screws (be sure to align it properly first)

Once the power supply is in place and secured, check the position of
the voltage selection switch, shown in Figure 26-7,
and reset it if necessary. Do not neglect this step. If the power
supply voltage switch is set to 220/240V and you connect the system
to 110/120V mains, nothing bad happens, though the system
doesn't run. But if your mains voltage is 220/240V
and you leave the power supply voltage switch set to 110/120V, you
can expect your motherboard and connected components to literally
burn to a crisp within a second of applying power to it. Some power
supplies are autosensing and so do not have a voltage selection
switch. But if yours does have such a switch, make sure to set it
properly before you connect any cables.

Figure 26-7. Setting the voltage selection switch for the correct local voltage

Once you have installed and secured the power supply and set the
voltage selection switch, reconnect the motherboard power cables and
all drive power cables. If your system has auxiliary fans that are
powered from power supply connectors, reconnect those too. Once
you've verified that everything is installed and
connected correctly, reconnect the main power cable and apply power
to the system.